This invention relates to preparation of electrophoresis gels.
Electrophoresis gels are generally cast by the user in the same enclosures in which they are held during the actual electrophoresis. When electrified buffer solutions are used to apply the potential across the gel, the enclosure must be open at each of two opposing ends to expose the gel to each solution. To cast the gel, of course, one of these open ends must be sealed off so that the gel forming solution can be added and held inside until it sets to form the gel.
In many cases among the many sizes and geometries of electrophoresis gels, it is a simple matter to seal off one of the two openings in such a manner that will prevent leakage and yet permit easy removal once the gel is cast. In others, however, this presents a problem, particularly when the enclosures comprise several parts clamped together. Slab gel enclosures consisting of a pair of flat plates separated by spacers are a prime example. DNA sequencing cells are particularly troublesome, since the plates are large and dimensionally inexact. The plates are made of glass, beveled at the edges to resist chipping. Both the size and the beveled edges make them difficult to align accurately. When poorly aligned plates are clamped together with spacers in between, commonly used casting stands equipped with gaskets are generally insufficient to establish a water tight seal at the lower end of the plates.
One alternative has been the use of sealing tape across the opening. This is difficult and time consuming, however, and runs the risk of contaminating the gel solution with the tape adhesive. Another alternative has been to insert a third spacer between the plates along the bottom edge. This results in a recessed gel, however, which is capable of entrapping air bubbles due to incomplete evacuation prior to electrophoresis, and of retaining air bubbles generated by the electrode during the electrophoresis itself.